When people performed addition, they triggered the same patterns of brain activity that light up when they looked right. When they did subtraction, the left-looking brain patterns activated.

Previous studies have shown that numbers and space perception are closely linked in the brain, and this new research could help explain why, said study leader Andre Knops of the French health organization INSERM in Gif-sur-Yvette.

The research might also lead to better ways of teaching math in schools, Knops added.

"Teachers could emphasize the link between numbers and space by making use of spatial relations between numbers," he suggested—although such approaches would first have to be validated and tested by educators.